Retromer dysfunction in amyotrophic lateral sclerosis.

Retromer is a heteropentameric complex that plays a specialized role in endosomal protein sorting and trafficking. Here, we report a reduction in the retromer proteins-vacuolar protein sorting 35 (VPS35), VPS26A, and VPS29-in patients with amyotrophic lateral sclerosis (ALS) and in the ALS model provided by transgenic (Tg) mice expressing the mutant superoxide dismutase-1 G93A. These changes are accompanied by a reduction of levels of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit GluA1, a proxy of retromer function, in spinal cords from Tg SOD1 ^G93A mice. Correction of the retromer deficit by a viral vector expressing VPS35 exacerbates the paralytic phenotype in Tg SOD1 ^G93A mice. Conversely, lowering Vps35 levels in Tg SOD1 ^G93A mice ameliorates the disease phenotype. In light of these findings, we propose that mild alterations in retromer inversely modulate neurodegeneration propensity in ALS.